In the field of semiconductor integrated circuit (IC) manufacturing, active semiconductor devices, e.g. transistors, are generally manufactured or formed by applying well-known front end of line (FEOL) technologies. A transistor may be a field-effect-transistor (FET), e.g. a complementary metal-oxide-semiconductor (CMOS) FET, and the FET may be a p-type doped FET (pFET) or an n-type doped FET (nFET). Different types of transistors may be manufactured on a common substrate of semiconductor chip or structure.
In most recent several years, efforts of continuing to scale FET devices have been mainly focused on the area of stress engineering. For example, in the case of manufacturing pFET devices, incorporation of compressive stress liners and/or stressors of embedded SiGe (eSiGe) in source and drain regions have successfully demonstrated improvement in performance of the pFET devices. In order to further enhance performance of the pFET devices, new techniques may need to be developed and incorporated into the existing FEOL technology and, in certain situations, careful optimization of current technology elements may need to be performed.
It is well-known in the art that increasing Ge concentration in the eSiGi as well as bringing eSiGe stressor closer to the channel region of a pFET device may result in certain desirably higher strain in the channel, which in turn may improve performance of the device. However, it is also known in the art that, with the current FEOL technology, there are certain practical limitations on the level of Ge concentration that may be used before strain relaxation occurs as well as limitations to the proximity that eSiGe stressor in the source and drain regions may be brought relatively close to the channel region.
Therefore, there exists in the art a need to develop new method, and structures associated with the method, to further enhance the strain effect of eSiGe stressor without degrading performance of a pFET such as, for example, parasitic and punch-through characteristics of the pFET.